Recently, small electronic apparatuses each containing an electric power generation system to operate without battery replacement have been achieved (for example, refer to PTL 1). Such an electronic apparatus has a function of temporarily charging electric power generated by the electric power generation system to a secondary battery, and when electric power is not generated, the electronic apparatus is driven by electric power discharged from the secondary battery. Moreover, small electronic apparatuses each capable of being connected to a small electric power generation unit having a similar function to that of the above-described electric power generation system have been achieved. In such an electronic apparatus connected to the above-described electric power generation unit, the electric power generation unit is allowed to charge electric power to a secondary battery contained in the electronic apparatus, or to directly drive the electronic apparatus.
Therefore, the above-described electronic apparatus is allowed to operate for a long time even in an environment without an outlet and a replacement battery. Accordingly, in view of emergencies such as earthquake disaster, it is expected that a large number of small electronic apparatuses contain the electric power generation system or a system capable of being connected to the small electric power generation unit.